What is the difference between a differential circuit breaker and an RCD? What do they protect against? Which type to choose in the apartment, in the kitchen? What is the difference between an RCD and a difavtomat? Examples of 4 differential protection markings.

TEST:

Mini-test on the safe use of RCDs.

1. What type of load is the protective device installed on?

A) for a washing machine

B) to the common line, to the apartment panel

1. What should be the operating current?

1. What type of RCD is used?

A) automatic differential

B) difrel and circuit breaker

1. What will the differential protection in this design protect against?

A) from electric shock

B) from a fire

Possible answers:

1. For the washing machine (A), we select an RCD with a response threshold of 10 mA (A), with the RCD type differential automatic (A). This threshold value protects against electrical injury (A).
2. Protection with a differential current value of 100 mA should be installed in the apartment panel (B). An RCD with a switch (B) will reduce the likelihood of a fire (B).
3. For a washing machine (A) with a threshold of 30mA (A), a differential relay with a machine (B) will protect against electric shock (A).

SIMPLE differences between a differential machine and a relay. We distinguish protection devices according to 4 characteristics.

Video 1. This video describes how to distinguish a differential machine from a relay.

As an example, we consider a difrel and an automatic machine from IEK.

“Formula” technical differences between RCD and difavtomat.

1st sign. Inscription on the device body. A differential switch means a difrele, and an automatic differential current switch means a differential circuit breaker (RCBO).

2nd sign. The presence of a letter (B, C, D or E - operating speed of the built-in switch) before the operating current value indicates the RCBO.

3rd sign. The diagram does not show a conventional representation of shutdown due to overload and short circuit.

4th sign. Previously, automatic machines were larger in size. Currently this sign is not typical.

Designation of ouzo and difavtomat on the diagrams.

In order to understand the diagram of complex panels, you need to know how the protection devices are shown on the diagram. As discussed above, the main device of the RCD was a difference current transformer that controls the breaking contacts. It is placed on the symbol, Fig. 5

Rice. 5. Single- and double-pole differential relay.

The RCBO, as we have already discussed, has one more active element - a circuit breaker. According to GOST 2.755-87 ESKD, it is designated by a rectangle on the breaking contact (Fig. 6).

Rice. 6. RCBO on the diagram.

IMPORTANT! The given examples of notations are of a conditional nature, because regulatory documents not regulated.

Let's look at the graphical symbols on part of the real circuit (Fig. 7).

Rice. 7. Designation of RCD in an excerpt from a real project.

In this scheme, the differential relay is switched on in the floor panel after the circuit breaker and the meter. Following the rules of GOST 2.710-81, each element of a single-line network, in addition to the graphic one, also has a letter designation t. In our case, the differential protection Q0 is of type F202.

What 2 dangers does an RCD protect against?

1st danger.

There are quite a lot of devices in our homes that operate on the network. Everyone knows that electric current is dangerous to humans. Under normal conditions, electricity does not pose a danger because... the housings of electrical appliances are insulated, and electric shock through the air is impossible. But there are two rooms in which current poses an increased danger. In the bathrooms there is a washing machine that has an electric motor and consumes significant power during operation. Also in the bathroom and kitchen, current flows through water. In this case (Fig. 1), a path for electricity through the human body is possible. This current, called leakage current (or differential), does not trip the circuit breaker in the panel, but is sufficient to cause severe electrical injury.

Rice. 1. If the phase wire (C) comes into contact with the washing machine body, there is a danger of electricity (red line) passing through the human body to ground (PE).

2nd danger

Current that flows uncontrollably from the electrical network leads to heating of conductive parts and can cause a fire.

The amount of electricity sufficient to cause injury and to cause a fire varies in magnitude. An RCD (diffuse protection) will help increase the safety of wiring by eliminating these 2 dangers. The differential protection has a fire-prevention effect when installed on groups of consumers (apartment or floor electrical panel). In other cases, the RCD is included in the power supply circuit of a specific consumer.

Definition. A residual current device is a device used to protect people and electrical devices from differential current.

TOP 3 premises with mandatory installation of differential protection:

1. Rooms with high humidity.
2. With metal floors.
3. Premises with devices having a conductive body.

Marking. Designation on the body of 5 main parameters.

Photo 1 shows a differential relay. On the front side of the device, next to the switch, you can see the parameter markings:

1. Operating current of the differential relay (16 A). The automatic transmission accompanying the differential relay should be no less important.
2. Short circuit current (3000) – the maximum value at which the relay retains its functionality.
3. Type of leak. This relay will operate when an alternating differential current appears.
4. Operating AC voltage and frequency (230 V 50 Hz).
5. Rated operating current (30 mA) – the minimum leakage current at which the consumer will turn off.

IMPORTANT! Also on the case there is information about the operating temperature.

1. – the device can be installed outside heated rooms – down to minus 25 degrees.

3 connection diagrams for differential circuit breakers and RCDs.

Let's consider three typical differential protection connection schemes.

1. Connecting a differential relay to a separate consumer.

Let's say we want to increase the electrical safety of an individual, most dangerous consumer by turning it on through an RCD (Fig. 2). The consumer is a washing machine installed in the bathroom.

Rice. 2. Washing machine connection line. Red wire – phase L, blue – neutral N, brown – protective grounding PE.

IMPORTANT! The "TEST" button, when pressed, opens the consumer's power supply circuit. This button is used to check the operation of the device.

In Figure 2, the input lines of the power supply network pass through the GA group automaton and are distributed to consumers through the meter. The washing machine is connected using an RCD and a separate circuit breaker AB installed in the phase wire L. A differential relay acts as a protective device in this circuit. Inside such a device, wires L and N pass inside the transformer T (These wires make up the primary winding I). The secondary winding II is connected to the comparison circuit A. The comparison circuit controls the operation of the polarized relay P, which can open the contacts K.

• Normal mode

Figure 2 shows normal operation - the washing machine is working correctly, there are no short circuits. All electricity passing through bus L returns through bus N. The current in winding II, which is equal to the difference in currents in the primary, is zero. The relay does not operate.

• Differential current and short circuit.

If the load malfunctions, electricity leaks (yellow dotted line) inside the washing machine body. A difference current occurs in transformer T of the protection device. Comparison circuit A through relay P disconnects the load from the network. If there is a short circuit in the machine, the AB circuit breaker turns off its line.

1. Connecting a differential machine to a common circuit.

Rice. 3. Introduction of a single RCD into the electrical wiring.

Inside the input panel (Fig. 3 green dotted line) there is an RCD - in this case a differential circuit breaker. Inside it, the phase conductor additionally passes through short-circuit protection (>I) and overload protection (t), as in a conventional circuit breaker. The power supply will be disconnected for any reason for a fire - excess consumption, short circuit to the load and the presence of differential current.

IMPORTANT! RCDs used as fire protection have a higher rated operating current.

1. We distribute differential protection into groups. Leaks of direct and alternating current.

If you install a separate differential automatic for each load - each chandelier, computer, TV, air conditioner, washing machine, then you will get the most expensive option. Using differential relays that respond to a certain leakage current, it will be possible to group consumers and reduce costs (Fig. 4)

Rice. 4. Loads are grouped. Protective grounding is not conventionally shown. After the meter, 50A circuit breakers are installed.

In Figure 4, a washing machine with a powerful AC motor is connected through an RCD with a current of 10 mA. Other loads - sockets, lighting, computer - are powered through a differential relay with an operating threshold of 30 mA. At the input, after the meter, a differential relay is switched on as a fire safety device.

How to avoid improper operation of the RCD?

1. Combining neutral conductors from different protections leads to false tripping.
2. When connecting zero and ground, the RCD will not disconnect the load at all, even if a leak occurs.

Answers to 5 frequently asked questions.

1. Our house does not have a separate protective grounding line. Will there be any benefit from installing a protective shutdown?

With such wiring, the differential protection will be able to protect against electric shock when touching simultaneously a faulty load and sewer or other metal pipes. If the insulation inside the device is damaged (short circuit to the housing), triggering won't happen.

1. What operating time should be provided by differential protection?

All shutdown devices must turn off the consumer when a leak occurs in no more than 0.3 seconds. It is better to choose shutdown devices with high performance.

1. If fast protective devices are the best, why are delayed tripping RCDs produced?

Such devices are installed on powerful electricity consumers. When they start or stop, an uncontrolled leakage of electricity may occur.

1. The use of protective shutdown is mainly advisory in nature. In what cases can you not do without it?

The PUE discusses several cases of mandatory use of differential protection. The most typical is the protection of mobile residential trailers and outdoor electrical consumers.

1. And in what cases is RCD not recommended?

In cases where disconnection can lead to a more dangerous result (installation of an alarm on the power line, medical devices)

Very often, inexperienced electricians and home craftsmen do not know how to determine what is in the panel - an RCD or a circuit breaker. As a result, one may mistakenly think that the electrical wiring is protected from overloads and current leakage, although in fact, protection is not provided against the first unsafe situation, because The panel contains a conventional residual current device. In this article, we will not only look at the functional difference between these two devices, but also tell you how to visually distinguish an RCD from a difavtomat.

Difference in function

Let us briefly describe how a residual current device differs from a differential circuit breaker. It's quite simple:

1. triggers only when . is detected in the circuit.
2. includes the functions of a residual current device + circuit breaker. In total, the differential circuit breaker is triggered not only during a current leak, but also during, and also.

This is the main functional difference between the two devices. You can find out in our corresponding article. Now we will tell you how to distinguish them by appearance.

Visual difference

Now, using photo examples, we will clearly show how to determine what exactly is installed in the panel. In total, we will tell you about 4 obvious signs that you need to remember.

Main Differences

So we have provided instructions for young electricians and home craftsmen. As you can see, in fact there is nothing complicated, and the difference between a residual current device and a differential circuit breaker is quite significant. We hope you now know how to visually distinguish an RCD from a difavtomat!

The main difference between an RCD (sometimes called a difrele) and a difavtomat lies in the decoding of the devices: an RCD is a trip protection device, a difavtomat is a differential (i.e., in this case, multifunctional) circuit breaker.

Technical principle of operation of RCD, difavtomat

A protective device (RCD) is an electrical device that includes a module for detecting the difference in currents that flow through the device. That is, if this difference does not correspond to the specified value, the contacts will open. To ensure this process, the RCD includes separate elements capable of detecting, measuring differential current and “making a decision” about opening the contacts. The last operation is performed by a disconnector that does not contain elements to protect the electrical circuit from short circuits or overloads.

A difavtomat is essentially a block that combines an RCD and a disconnect device. The machine protects the electrical circuit from current leakage (similar to an RCD) and at the same time interrupts the power supply in the event of a short circuit (short circuit) or overload. The performance of such functions is ensured by the presence in the automatic circuit breaker of protection against overheating and overcurrent, which guarantees the protection of the circuit and equipment.

The difference between a difavtomat and an RCD

The function of the protective device is to turn off the electrical circuit only in the event of a current leakage, i.e. it is simply a device connected to a network that requires protection. The RCD is a module that detects current leakage (for example, when insulation is damaged) and commands the power mechanism to turn off the circuit. At the same time, the RCD cannot protect the network from overloads or short circuits. Simply put, if a short circuit occurs in your electrical wiring or all load standards are exceeded, all the wires will burn out along with the RCD.

A differential machine is an electrical assembly that includes protection against current leakage and protection against short circuits, plus overloads. At the same time, the automatic rifle also protects itself. Both devices can be distinguished visually. The difrel has a designation in large letters; for example, "16A" indicating the current rating. If on the body of the device there is a Latin letter in front of the large number, for example, “C16”, then in front of you is a difavtomat (“C” characterizes the type of release designed for 16A). If the devices have symbols in Russian, then “VD” will mean that you have an RCD, but if it says AVDT, then this is a “differential-type circuit breaker.”

As mentioned above, these devices have different functions; they are similar only in the type of fastening and in appearance.

What is the difference between an RCD and an automatic machine?

Circuit breaker

- this is the creation of protection for electrical wiring from damage due to short circuits and long-term overcurrent. Without an automatic machine, the electrical wiring would have to be changed very often, because short-circuit currents would melt the wires, and overload currents would burn all the insulation of the wires.

The machine contains electromagnetic protection against high short-circuit currents. It is an electromagnetic coil with a core.

At the moment of a short circuit, the coil creates an electromagnetic field and magnetizes the core, which causes it to push the trigger latch and the machine turns off. If overload currents arise, the bimetallic plates, heating and bending, move the levers and force the trigger mechanism to operate.

Automatic switch ABB

The shutdown time of the overload protection directly depends on the strength of the overload current. The machine body also contains an arc-extinguishing chamber, which is designed to extinguish the spark and increase the service life of the contacts.

Residual current device and its operation

The difference between an RCD and a circuit breaker is that it has a leakage current protection function; a circuit breaker does not have such protection. The RCD contains a differential transformer, which determines the difference in the current of the phase and neutral wires during current leakage.

These currents, amplified by the secondary winding of the differential transformer, are supplied to a polarized relay associated with the trigger, which turns off the protection. Thus, the RCD device is protected against leakage currents.

Residual current devices

Leakage currents can occur when the insulation of a wire breaks down on the housing of electrical household appliances and a person touches it. In this case, this type of protection saves a person’s life. The operation of the RCD is based on determining the difference between the phase and zero currents, so it has two terminals for connecting the phase and zero, and two more terminals for the phase and zero output for connecting the load.

That is, this device is two-pole for a single-phase network, and four-pole for a three-phase network. Also, an RCD differs from a simple machine in that it has a test button to check its functionality. The machine for a single-phase network has a single-pole module, and for a three-phase network it has a four-pole module.

How to properly connect an RCD and a machine

The RCD does not provide protection against short circuits, as well as against overload, therefore, in order for the protection device not to fail, a machine with a rated current lower than the rated current of the RCD must be placed in front of the RCD by one or two orders of magnitude.

Correct connection diagram for Uzo in an apartment panel. After the introductory circuit breaker VA - 47/50A there is an EKF RCD 2/63A/30mA

An example - and a machine - if there is a 50 A machine, then you need to install a 63 A RCD. Thus, we decided the question of what to install, the machine before the RCD or after. The answer is clear, the machine is placed in front of the RCD in order to protect it, de-energize it in time and preserve the device.

Content:

Quite often, when equipping home electrical networks, you have to decide whether an RCD or a circuit breaker is better, what to choose and how to connect. In order to make the right decision, it is necessary to know the main functions of each protective device. Both devices are capable of creating safe conditions for work and living, providing protection from electric shock, subject to correct selection, connection and further operation.

Functions of a differential machine

Differential circuit breakers belong to the category of protective devices that perform simultaneous shutdown in the event of emergency situations. These devices are capable of simultaneously monitoring the presence of short circuits and current leaks, turning off the power in both cases.

The difavtomats successfully combine the functions of a standard circuit breaker and a residual current device. The main purpose of the difavtomat is protection in case of contact with exposed wires or parts of equipment that are energized due to any damage. Differential circuit breakers are designed for different ratings of operating currents and leakage currents.

Each device is divided into two functional parts. This includes a two- or four-pole circuit breaker and a module that protects against electric shock. A DIN rail is used to mount the device, which allows it to take up less space in the panel compared to individual devices ().

All differential machines have a speed of only 0.04 seconds. This ensures adequate replacement of the RCD and protection against electric shock. These devices play an important role in protecting various devices and equipment from overloads that occur during emergency situations. The design of the difavtomat allows you to quickly turn off the power to any part of the network during voltage surges of more than 250 volts.

Thus, differential automatic machines have a high response speed. They are able to effectively protect equipment during operational overloads and power surges. These protective devices can be operated in the temperature range from -25 to +500C, they have a high wear resistance threshold. In fact, an RCD with a machine in one housing made it possible to obtain a separate protective device with advanced functions.

Features of RCD operation

The main function of the RCD is instantaneous operation when leakage currents appear, as a result, the electrical network is disconnected from the power source. These systems are installed on, as well as on dedicated lines of household appliances and other equipment. RCDs are not designed to protect against short circuits and system overloads. Some electricians do not take this fact into account, using only RCDs in circuits in order to reduce their cost.

The basis of the device is a current sensor that responds to a changing differential current in the conductors. It is made in the form of a conventional transformer with a toroidal core. The response threshold level is set using a magnetoelectric relay, which has high sensitivity to all changes. This scheme, characteristic of most RCDs, ensures ease of operation, reliability and safety in operation. Modern devices are represented by electronic models using special electronic circuits.

The actuator includes the contact group itself, which is set to the maximum current value. In case of any problems in the circuit, a special contact group is used that operates to open. The functionality of the device is checked by pressing the TEST button. After this, an artificial current is supplied to the secondary winding, which causes the relay to operate.

Many owners of apartments and private houses are wondering whether to choose an RCD or a difavtomat. There are certain recommendations from experts on the use of differential automatic machines. They are most suitable for simple networks in which circuit breakers will not be installed for each group of consumers. In such cases, they are installed at the entrance after the electric meter instead of the RCD. Differential protection is ideal for powerful consumers, lines laid in basements, bathhouses, for street lighting and other separately located objects.

What is the difference between an RCD and a differential circuit breaker?

Externally, both devices are very similar to each other. However, these are two different devices, with their own functions. The RCD is not able to protect the circuit from short circuits or overloads. For this purpose, it is necessary to use a circuit breaker installed in front of the residual current device. This is how the RCD differs from the differential circuit breaker.

Therefore, preference is often given to a difavtomat, which combines the functions of not only an RCD, but also a circuit breaker. It is able to protect against, save equipment and wiring from short circuits. Since these are two different devices, you need to be careful when purchasing a specific protective device.

• First of all, the exact name of the device is determined in order to find out whether it is a differential circuit breaker or an RCD.
• It is better to use products from well-known manufacturers, since the labeling of Chinese products very often does not correspond to reality.
• Domestic manufacturers apply the name of the device directly on the side of the device.
• If on the case there are only numbers corresponding to the rated current in amperes, then this is an RCD. When there is a letter marking in front of the numbers, B, C or D is a differential circuit breaker, and the letters correspond to the characteristics of the thermal and electromagnetic releases.
• When deciding whether to use an RCD or a differential circuit breaker for an apartment, you need to pay attention to the dimensions of both devices. In addition, you need to look at the connection diagram. If the word TEST is written without additional characters, this is an RCD; if next to this word there is a designation of the windings of the releases, this is a difavtomat.
• There is a mark on the RCD indicating the rated current or maximum permissible load.
• The main characteristic of the difavtomat is the response time, designated as C16, etc.

Additionally, it will help to distinguish what it is, a difavtomat or an RCD, printed on the device. On the front side of the RCD there is an image of only a differential transformer, and on the differential circuit breaker circuits of two releases are added.

What to choose RCD or difavtomat

The choice of one or another protective device is carried out in accordance with their distinctive features, most suitable for specific operating conditions. The question of which is better: an RCD or a differential circuit breaker usually arises during repairs, when, in addition to construction work, all electrical equipment is replaced.

It is impossible to give an exact answer, since each device is used for specific purposes. We must not forget about the possibilities of installing it in an electrical panel. Many owners prefer compact distribution panels with small dimensions. In such cases, installing an additional device creates a serious problem. For example, a differential circuit breaker requires two modules, while the RCD and the circuit breaker require three modules.

During operation, when a differential circuit breaker is triggered, it is sometimes difficult to determine the cause. This could be a current leak or a short circuit. The RCD and circuit breaker trip on their own and indicate exactly what factors caused this to happen. The most advanced modern automatic machines are equipped with signal flags indicating the activation of a specific element of the device.

The reliability of the device is of great importance, which largely depends on the manufacturer. Accordingly, the price of the products will also differ. In the event of a malfunction, you will have to completely change the automatic circuit breaker, and in the combination of the RCD-automatic device you will need to replace only one of the faulty parts.

The best RCDs

When deciding what to choose to protect the electrical network - a machine with an RCD or a difautomatic machine, you should pay attention to the manufacturers of these products. Currently, the highest quality products are produced in Europe and the USA. Among them, ABB (Switzerland and Sweden), Legrand and Schneider Electric (France), General Electric (USA) and many others are widely popular. RCDs from these manufacturers have a relatively high price. The quality of products from domestic manufacturers is much lower, but their price is also low, which in many cases is of decisive importance. Our RCDs are quite reliable in operation, as evidenced by numerous positive reviews.